An ultrasound system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound system has been extensively used in the medical profession. Modern high-performance ultrasound systems and techniques are commonly used to produce two or three-dimensional images of internal features of an object (e.g., human organs).
The ultrasound system employs an ultrasound probe containing a transducer array for transmission and reception of ultrasound signals. The ultrasound signals are transmitted along scan lines aligned with a direction of a scan head of the ultrasound probe. The ultrasound system forms ultrasound images based on the received ultrasound signals. Recently, the technique of transmitting the ultrasound signals by steering scan lines at multiple steering angles to obtain multiple ultrasound images and spatially compounding the ultrasound images (spatial compound imaging) has been used to obtain an enhanced ultrasound image.
Generally, the probe may include a lens formed on a transducer array for focusing the ultrasound signals. When the ultrasound signals, which are generated from the transducer array, are transmitted to the target object along scan lines steered at a predetermined steering angle, the ultrasound signals may be refracted due to a difference in velocity of sound when the ultrasound signals pass through the lens and when the ultrasound signals pass the target object. Also, a velocity difference may be caused when the ultrasound signals propagate through various tissues in the target object. The refraction may cause distortion of directivity of echo signals and errors in estimating locations and azimuth of ultrasound data. Thus, when the ultrasound images formed at different multiple steering angles are spatially compounded to form a spatial compound image, mis-registration between the ultrasound images may occur. Thus, blurring may appear in the spatial compound image.